Phthalate esters are plasticizers incorporated into nearly all plastic materials. The biochemical and ultrastructural effects of di(2-ethylhexyl)phthalate (DEHP) and related chemicals on the rodent liver are being studied in order to assess potential mechanisms of phthalate ester hapatocarcinogenicity. DEHP is also a male chemosterilant and is teratogenic in mice. Studies are being conducted to determine the role of zinc in the pathophysiology of these reproductive effects and to discern no-observed toxic effect levels.